1. Field
The present invention relates to the thermal management of a battery charging system. Controlling the heat flow from the circuit that converts analog power to a digital charging pulse to the battery under charge is necessary to ensure a fast and complete charge without any degradation of that battery. Lithium ion batteries are particularly susceptible to the influences of temperature while under charge and are typically required to have their charging suspended when the battery temperature reaches 45° Celsius.
2. Description of Related Art
There have been previous attempts to control the heat transferred from the charging circuit to the batteries under charge. Some designs have ignored the problem of the heat from charging circuit components reaching the battery(s) under charge and have modified their battery charging parameters to keep the lithium-ion battery temperatures within the recommended limits. In the past voltages and charging cycles are adjusted when the temperature of the battery under charge had reached certain limits. This, however, increased the time required to charge the battery, added cost, complexity and another potential failure point of the charging unit. Other approaches included adding cooling fins to the unit to transfer the heat generated by the charging circuit. However this added weight and size to the battery charger and the amount of heat carried away is largely dependent on the ambient temperature and the amount of air flow circulating around the fin. Another approach included adding fans to transfer the heat generated by the charging circuit away from the battery. Fans also add complexity, and another heat load.